Margin derivation from intrafraction patient motion of multi-target, single isocentre, brain stereotactic radiosurgery treatments.

BACKGROUND: Brain metastases are the most common intracranial malignancy and remain a substantial source of morbidity and mortality in cancer patients. Linear accelerator based stereotactic radiosurgery (SRS) is widely used and is frequently delivered by hypo-fractionnated volumetric modulated arc therapy using non-coplanar beams, where geometric accuracy and planning margins are a major concern. PURPOSE: To give a practical analysis of intrafraction patient motion for multi-target, single isocentre, brain SRS treatments and to derive adapted GTV-to-PTV margins. METHODS: Data of 154 lesions, spread over 85 fractions from 56 patients treated in our institution with the Varian HyperArc  SRS solution was processed. Intrafraction patient motion were recorded using an Optical Surface Monitoring System during irradiation. The present study focuses on small tumor volumes, roughly equal or inferior to 1.5  cm 3 ${\rm cm}^3$ , and frameless mask-based immobilization. For each treatment session, a tumor displacement vector matrix was calculated from the patient drifts as a function of time. Data were combined together into a representative treatment scenario and the dosimetric impact of GTV displacement was calculated. RESULTS: Recommended margins due to patient motion range between 0.3 and 1 mm, depending on the distance tumor-isocentre, and the desired GTV edge dose coverage. Those values should be added quadratically with other sources of uncertainty, such as mechanical isocentre and kV-MV misalignment. CONCLUSION: Thorough analysis of intrafraction patient motion was performed, the dosimetric impact was calculated for different scenarios, and adequate GTV-to-PTV margins were derived. These values vary according to the distance isocentre-to-GTV, as well as the desired dose coverage, and should be chosen adequately.

Designing clinical trials based on modern imaging and metastasis-directed treatments in patients with oligometastatic breast cancer: a consensus recommendation from the EORTC Imaging and Breast Cancer Groups.

Breast cancer remains the most common cause of cancer death among women. Despite its considerable histological and molecular heterogeneity, those characteristics are not distinguished in most definitions of oligometastatic disease and clinical trials of oligometastatic breast cancer. After an exhaustive review of the literature covering all aspects of oligometastatic breast cancer, 35 experts from the European Organisation for Research and Treatment of Cancer Imaging and Breast Cancer Groups elaborated a Delphi questionnaire aimed at offering consensus recommendations, including oligometastatic breast cancer definition, optimal diagnostic pathways, and clinical trials required to evaluate the effect of diagnostic imaging strategies and metastasis-directed therapies. The main recommendations are the introduction of modern imaging methods in metastatic screening for an earlier diagnosis of oligometastatic breast cancer and the development of prospective trials also considering the histological and molecular complexity of breast cancer. Strategies for the randomisation of imaging methods and therapeutic approaches in different subsets of patients are also addressed.

A patterns of care analysis of hyperthermia in combination with radio(chemo)therapy or chemotherapy in European clinical centers.

PURPOSE: The combination of hyperthermia (HT) with radio(chemo)therapy or chemotherapy (CT) is an established treatment strategy for specific indications. Its application in routine clinical practice in Europe depends on regulatory and local conditions. We conducted a survey among European clinical centers to determine current practice of HT. METHODS: A questionnaire with 22 questions was sent to 24 European HT centers. The questions were divided into two main categories. The first category assessed how many patients are treated with HT in combination with radio(chemo)therapy or CT for specific indications per year. The second category addressed which hyperthermia parameters are recorded. Analysis was performed using descriptive methods. RESULTS: The response rate was 71% (17/24) and 16 centers were included in this evaluation. Annually, these 16 centers treat approximately 637 patients using HT in combination with radio(chemo)therapy or CT. On average, 34% (range: 3-100%) of patients are treated in clinical study protocols. Temperature readings and the time interval between HT and radio(chemo)therapy or CT are recorded in 13 (81%) and 9 (56%) centers, respectively. The thermal dose quality parameter "cumulative equivalent minutes at 43 °C" (CEM43°C) is only evaluated in five (31%) centers for each HT session. With regard to treatment sequence, 8 (50%) centers administer HT before radio(chemo)therapy and the other 8 in the reverse order. CONCLUSION: There is a significant heterogeneity among European HT centers as to the indications treated and the recording of thermometric parameters. More evidence from clinical studies is necessary to achieve standardization of HT practice.

Circulating immune cell populations related to primary breast cancer, surgical removal, and radiotherapy revealed by flow cytometry analysis.

BACKGROUND: Advanced breast cancer (BC) impact immune cells in the blood but whether such effects may reflect the presence of early BC and its therapeutic management remains elusive. METHODS: To address this question, we used multiparametric flow cytometry to analyze circulating leukocytes in patients with early BC (n = 13) at the time of diagnosis, after surgery, and after adjuvant radiotherapy, compared to healthy individuals. Data were analyzed using a minimally supervised approach based on FlowSOM algorithm and validated manually. RESULTS: At the time of diagnosis, BC patients have an increased frequency of CD117+CD11b+ granulocytes, which was significantly reduced after tumor removal. Adjuvant radiotherapy increased the frequency of CD45RO+ memory CD4+ T cells and CD4+ regulatory T cells. FlowSOM algorithm analysis revealed several unanticipated populations, including cells negative for all markers tested, CD11b+CD15low, CD3+CD4-CD8-, CD3+CD4+CD8+, and CD3+CD8+CD127+CD45RO+ cells, associated with BC or radiotherapy. CONCLUSIONS: This study revealed changes in blood leukocytes associated with primary BC, surgical removal, and adjuvant radiotherapy. Specifically, it identified increased levels of CD117+ granulocytes, memory, and regulatory CD4+ T cells as potential biomarkers of BC and radiotherapy, respectively. Importantly, the study demonstrates the value of unsupervised analysis of complex flow cytometry data to unravel new cell populations of potential clinical relevance.

Locoregional Control and Toxicity in Head and Neck Carcinoma Patients following Helical Tomotherapy-Delivered Intensity-Modulated Radiation Therapy Compared with 3D-CRT Data.

OBJECTIVES: To assess the feasibility and efficacy of intensity-modulated radiation implemented with helical tomotherapy image-guided with daily megavoltage computed tomography for head and neck cancer. METHODS: Between May 2010 and May 2013, 72 patients were treated with curative intent. The median age was 64 years, with 57% undergoing definitive and 43% postoperative radiotherapy. Primary tumour sites were oral cavity (21%), oropharynx (26%), hypopharynx (20%), larynx (22%), and others (11%). Staging included 4% stage I, 15% II, 26% III, 48% IVa, and 7% IVb. Radiotherapy was combined with chemotherapy in 64%. Primary endpoint was locoregional control, and secondary endpoints survival and toxicity. RESULTS: Median follow-up was 20 months, with 11 locoregional recurrences. Three-year disease-free survival was 58% and overall survival 57%. In the multivariate analysis, age under 64 years, no extracapsular extension, postoperative radiotherapy, induction chemotherapy, and non-oral cavity tumour were significant favourable prognostic factors for disease-free-survival. The overall incidence of acute grade ≥3 toxicities were mucositis 32%, pain 11%, xerostomia 7%, dysphagia 53%, radiodermatitis 44%, and osteonecrosis 1%. Late grade ≥3 toxicities were fibrosis 6%, dysphagia 21%, fistula 1%, and skin necrosis 1%. CONCLUSIONS: Intensity-modulated radiation with helical tomotherapy achieved respectable locoregional control and overall survival, with acceptable toxicity, in head and neck cancer patients.

Hyperthermia and radiotherapy: physiological basis for a synergistic effect.

In cancer treatment, mild hyperthermia (HT) represents an old, but recently revived opportunity to increase the efficacy of radiotherapy (RT) without increasing side effects, thereby widening the therapeutic window. HT disrupts cellular homeostasis by acting on multiple targets, and its combination with RT produces synergistic antitumoral effects on specific pathophysiological mechanisms, associated to DNA damage and repair, hypoxia, stemness and immunostimulation. HT is furthermore associated to direct tumor cell kill, particularly in higher temperature levels. A phenomenon of temporary resistance to heat, known as thermotolerance, follows each HT session. Cancer treatment requires innovative concepts and combinations to be tested but, for a meaningful development of clinical trials, the understanding of the underlying mechanisms of the tested modalities is essential. In this mini-review, we aimed to describe the synergistic effects of the combination of HT with RT as well as the phenomena of thermal shock and thermotolerance, in order to stimulate clinicians in new, clinically relevant concepts and combinations, which become particularly relevant in the era of technological advents in both modalities but also cancer immunotherapy.

Electron radiation therapy: Back to the future?

Electron radiotherapy has long been preferred to photons for the treatment of superficial lesions because of its physical characteristics (high dose at the surface, rapid decrease in depth). Other characteristics (penumbra, heterogeneity on an oblique or irregular surface) make them difficult to use. In most indications (skin cancers, head and neck, medulloblastoma), with technical progress, in some cases they have been replaced by intensity-modulated conformal radiotherapy, brachytherapy and contact therapy. Other indications (drainage of mesotheliomas or irradiation of benign lesions) have disappeared. The low frequency of use leads to problems of safety and cost-effectiveness. However, modern photon radiotherapy techniques are still less effective than electrons in specific indications such as total skin irradiation (mycosis fungoides) or certain thin chest wall irradiations after total mastectomy, reirradiation or paediatric treatments without protons. Flash therapy, initiated by electrons, has been developed over the last 10 years, providing high-dose irradiation in an extremely short time. Initial results show good efficacy, with fewer side effects than with conventional radiotherapy. These results are leading to clinical technological developments on a larger scale. Although it has been replaced in most indications by more modern techniques, electron radiotherapy remains essential for targeted indications in specialised centres. The emergence of flash therapy will lead to new indications, on machines equipped with this new technology, which have yet to be defined and are currently the responsibility of specialised teams.

Health-related quality of life in men with oligometastatic prostate cancer following metastases-directed stereotactic body radiotherapy: Real-world data from the E2-RADIatE OligoCare cohort.

Objective: To evaluate the impact of metastases-directed stereotactic body radiotherapy (SBRT) on health-related quality of life (HRQoL) in men with oligometastatic prostate cancer (PCa) using real-world data from the OligoCare cohort. Materials and methods: OligoCare is a pragmatic, observational cohort designed to assess the impact of metastases-directed SBRT on patients with oligometastatic disease (OMD). We report an interim analyses of the secondary endpoint HRQoL, assessed using the EORTC QLQ-C30, within six months of metastases-directed SBRT for oligometastatic disease in men with PCa among the first 1600 registered patients. HRQoL data collection was optional within the OligoCare cohort. To compare HRQoL between baseline and first follow-up assessment, a Wilcoxon signed-rank test was used. A multiple linear regression model was used to explore the HRQoL associations with predefined factors. Results: Out of the 1600 registered patients, 658 were treated for oligometastatic PCa, of which 233 had baseline QoL data and 132 patients had both baseline and follow-up HRQoL data. At baseline, most patients had a WHO performance status of 0 or 1 (87 %), were de-novo oligometastatic (79 %), had one metastasis (90 %), and had a good overall global health status (mean 80.81, SD16.11, IQR 75-92). 51 % received hormonal therapy as concomitant systemic treatment. Patients with comorbidities as assessed by the Charlson Comorbidity index had a worse global health status at baseline (-4.88, 95 % CI:-9.35, -0.42). No clinically meaningful significant difference in global health status was observed at first assessment following SBRT (median 3.0 months) compared with baseline (mean difference 2.27, 95 % CI:-1.54, 6.08). Upon evaluating the proportions, meaningful clinically important differences (a 10-point or more difference) was observed in, 17 % and 11 % of the patients reporting deterioration and improvement of global health status, respectively. Conclusion: Metastases-directed stereotactic body radiotherapy had no negative impact on global HRQoL within the first six months after treatment.

Bilateral metallic hip implants: Are avoidance sectors necessary for pelvic VMAT treatments?

PURPOSE: Metallic hip implants (MHI) are common in elderly patients. For pelvic cancers radiotherapy, conventional approaches consist of MHI avoidance during treatment planning, which leads, especially in case of bilateral MHI, to a decreased quality or increased complexity of the treatment plan. The aim of this study is to investigate the necessity of using avoidance sectors (AvSe) using a 2-arcs coplanar pelvic volumetric modulated arc-therapy (VMAT) planning. METHODS: We evaluated: (1) The dose calculation error of a static 6MV open beam traversing a MHI; (2) The magnitude of an error's decrease within the planning target volume (PTV) for a 360° VMAT treatment without AvSe as compared to the static open beam; (3) The dosimetric influence of MHI misalignment generated by patient's repositioning rolls during image-guided radiotherapy (IGRT). RESULTS: (1) In the static 6MV beam configuration, for distances between 0.5cm and 6cm from the MHI, the median (maximum, number of points) dose calculation error was -1.55% (-2.5%, 11); (2) Compared to the static open beam, in the 360° VMAT treatment without AvSe a simulated error was decreased by a factor of 4.4/2.4 (median/minimum); (3) MHI anterior-posterior misalignment exceeding 0.6cm, resulted in error at PTV surface of >2%. CONCLUSIONS: A standard 2 coplanar arcs 360° VMAT treatment, with dedicated artifact reduction algorithms applied, decreased the error of static beam traversing MHI, in patients presenting a bilateral MHI and might be used to treat the pelvic region without MHI avoidance.

Sex-Specific Differences in Toxicity Following Systemic Paclitaxel Treatment and Localized Cardiac Radiotherapy.

The impact of sex in the development of long-term toxicities affecting the quality of life of cancer survivors has not been investigated experimentally. To address this issue, a series of neurologic and cardiologic endpoints were used to investigate sex-based differences triggered by paclitaxel treatment and radiotherapy exposure. Male and female wild-type (WT) mice were treated with paclitaxel (150 and 300 mg/kg) administered weekly over 6 weeks or exposed to 19 Gy cardiac irradiation. Cohorts were analyzed for behavioral and neurobiologic endpoints to assess systemic toxicity of paclitaxel or cardiovascular endpoints to assess radiotherapy toxicity. Interestingly, female WT mice exhibited enhanced tolerance compared to male WT mice regardless of the treatment regimen. To provide insight into the possible sex-specific protective mechanisms, rhoB-deficient animals and elderly mice (22 months) were used with a focus on the possible contribution of sex hormones, including estrogen. In females, RhoB deficiency and advanced age had no impact on neurocognitive impairment induced by paclitaxel but enhanced cardiac sensitivity to radiotherapy. Conversely, rhoB-deficiency protected males from radiation toxicity. In sum, RhoB was identified as a molecular determinant driving estrogen-dependent cardioprotection in female mice, whereas neuroprotection was not sex hormone dependent. To our knowledge, this study revealed for the first time sex- and organ-specific responses to paclitaxel and radiotherapy.

Single-fraction prostate stereotactic body radiotherapy: Dose reconstruction with electromagnetic intrafraction motion tracking.

PURPOSE: To reconstruct the dose delivered during single-fraction urethra-sparing prostate stereotactic body radiotherapy (SBRT) accounting for intrafraction motion monitored by intraprostatic electromagnetic transponders (EMT). METHODS: We analyzed data of 15 patients included in the phase I/II "ONE SHOT" trial and treated with a single fraction of 19 Gy to the planning target volume (PTV) and 17 Gy to the urethra planning risk volume. During delivery, prostate motion was tracked with implanted EMT. SBRT was interrupted when a 3-mm threshold was trespassed and corrected unless the offset was transient. Motion-encoded reconstructed (MER) plans were obtained by splitting the original plans into multiple sub-beams with isocenter shifts based on recorded EMT positions, mimicking prostate motion during treatment. We analyzed intrafraction motion and compared MER to planned doses. RESULTS: The median EMT motion range (±SD) during delivery was 0.26 ± 0.09, 0.22 ± 0.14 and 0.18 ± 0.10 cm in the antero-posterior, supero-inferior, and left-right axes, respectively. Treatment interruptions were needed for 8 patients because of target motion beyond limits in the antero-posterior (n = 6) and/or supero-inferior directions (n = 4). Comparing MER vs. original plan there was a median relative dose difference of -1.9% (range, -7.9 to -1.0%) and of +0.5% (-0.3-1.7%) for PTV D98% and D2%, respectively. The clinical target volume remained sufficiently covered with a median D98% difference of -0.3% (-1.6-0.5%). Bladder and rectum dosimetric parameters showed significant differences between original and MER plans, but mostly remained within acceptable limits. CONCLUSIONS: The dosimetric impact of intrafraction prostate motion was minimal for target coverage for single-fraction prostate SBRT with real-time electromagnetic tracking combined with beam gating.

Optimal sequence of implied modalities in the adjuvant setting of breast cancer treatment: an update on issues to consider.

The adjuvant setting of early breast cancer treatment is an evolving field where different modalities must be combined to improve outcomes; moreover, quality of life of breast cancer survivors emerges as a new important parameter to consider, thus implying a better understanding of toxicities of these modalities. We have conducted a review focusing on the latest literature of the past 3 years, trying to evaluate the existing data on the maximum acceptable delay of radiotherapy when given as sole adjuvant treatment after surgery and the optimal sequence of all these modalities with respect to each other. It becomes evident radiotherapy should be given as soon as possible and within a time frame of 6-20 weeks. Chemotherapy is given before radiotherapy and hormone therapy. However, radiotherapy should be started within 7 months after surgery in these cases. Hormone therapy with tamoxifen might be given safely concomitantly or sequentially with radiotherapy although solid data are still lacking. The concurrent administration of letrozole and radiotherapy seems to be safe, whereas data on trastuzumab can imply only that it is safe to use concurrently with radiotherapy. Randomized comparisons of hormone therapy and trastuzumab administration with radiotherapy need to be performed.

Postoperative accelerated radiotherapy with cytoprotection followed by three-dimensional conformal boost in patients with early endometrial/cervical cancer.

AIMS AND BACKGROUND: Adjuvant external beam radiotherapy is highly recommended for uterine carcinomas invading beyond the inner half of the myometrium or cervical stage IIa carcinomas. The addition of a booster intracavitary dose is widely used. METHODS: We assessed the feasibility and toxicity of a hypofractionated accelerated conformal radiotherapy scheme (2.7 Gy per fraction, for 14 consecutive fractions to the pelvis) supported with the cytoprotective agent amifostine (HypoARC). The amifostine dose was individualized (500-1000 mg daily subcutaneously). A booster dose of radiation was given to the vagina and stump using a 6-field 3D-conformal technique (3 x 4 Gy or 4 x 3 Gy) instead of intracavitary radiotherapy. RESULTS: Grade 2 diarrhea appeared in 9/25 (36%) and grade 1 cystitis in 7/25 (28%) cases. Analysis according to the amifostine dose level clearly showed reduced toxicity in patients receiving a daily dose of 750-1000 mg (P < 0.009). Within a median follow-up of 31 months (range, 11-52), there was only one case with grade 2 colitis (the patient had received no amifostine). None of the patients treated has relapsed locally or to distant organs within a median of 31 months of follow-up. CONCLUSIONS: It is concluded that HypoARC followed by 3D-conformal booster dose to the vagina is feasible and convenient for patients and for busy radiotherapy departments, as it reduces the overall time by 50%. When supported by high-dose daily amifostine, it has an impressively low rate of early and late radiation toxicity.

Hypofractionated/accelerated radiotherapy with cytoprotection (HypoARC) combined with vinorelbine and liposomal doxorubicin for locally advanced non-small cell lung cancer (NSCLC).

BACKGROUND: Combined radiochemotherapy is the gold standard for patients with locally advanced non-small cell lung cancer (LA-NSCLC). In the present study, the feasibility of hypofractionated accelerated radiotherapy with cytoprotection (HypoARC) in combination with vinorelbine and liposomal doxorubicin was evaluated. PATIENTS AND METHODS: Fourteen patients (pts) with LA-NSCLC (PS 0-2) were recruited. Patients received 15 fractions for 3.5 Gy within four consecutive weeks (1 week split after the 10th fraction), supported with subcutaneously administered amifostine (500-1000 mg/day). Pegylated liposomal doxorubicin was administered at a standard dose of 20 mg/m2 every two weeks, for 3 consecutive cycles. Vinorelbine was administered at 3 dose levels: a) 20 mg/m2 every week (5 pts), b) 25 mg/m2 thrice every two weeks (5 pts) and c) 30 mg/m2 thrice every two weeks (4 pts). RESULTS: Grade 3 neutropenia enforcing chemotherapy delays was noted in 2/5 and 2/4 patients in the groups b and c respectively. Fatigue was a common but not dose-defining feature. Radiation grade 2 esophagitis was noted in 6/14 patients. No case of severe radiation pneumonitis was noted. Partial response was documented in 9/14 patients, minimal response in 3/14 and stable disease in 2/14. The median local progression-free survival was 12 months and the median overall survival was 8 months. CONCLUSION: It is concluded that the administration of 25 mg/m2 of vinorelbine thrice a week together with liposomal doxorubicin and thoracic radiotherapy is feasible for patients with LA-NSCLC, providing high response rates. Further studies are required to better assess benefits in terms of local and distant control of the disease.

Spirometric values in Gypsy (Roma) children.

Values of spirometry indices vary among subjects of similar age, gender and somatometrics but of different ethnic origins. Low socioeconomic status in childhood is inversely related to lung growth. The aim of this investigation was to assess spirometry values in Gypsy children and compare them to reported values for Caucasians. Gypsy students attending primary schools in Central Greece were recruited. Spirometry indices were measured using a portable spirometer. Regression analysis was applied to construct prediction equations for forced vital capacity (FVC) and other spirometric indices (FEV(1), FEF(50), FEF(25), FEF(25-75)) based on standing height. Predicted spirometric values were compared to values for Caucasians from published studies. In 152 children (ages 5-14 years; 57 girls) lung function increased linearly with height: spirometry index=intercept+[slopexheight], (r(2)=0.68 for FVC and FEV(1) in girls; r(2)=0.78 for FVC and r(2)=0.74 for FEV(1) in boys). Excluding boys-but not girls-in puberty increased fit for FVC (r(2)=0.83) and FEV(1) (r(2)=0.79). Mean predicted values were 5-10% lower than values for Caucasians. In Gypsy children, FVC and expiratory flow function increase linearly with standing height and predicted values are lower than those for Caucasians of similar height.

A plesiotherapy technique for the post-operative treatment of skin cancer using Ir192 microSelectron.

We describe a technique of postoperative irradiation of skin cancer using plesiotherapy with Ir192 high dose rate microSelectron afterloading system (Nucletron, Veenendaal, Netherlands). The clinically defined area is drawn on the skin and the flexible 'skin applicator' is then orientated so that the drawn skin area is encompassed within the catheter defined surface. Using a thin pewter wire, the skin drawn area is copied on the air-adjacent surface of the applicator. Ex vivo CT simulation follows. The data are then transferred to the radiotherapy planning computer and the catheters are virtually reconstructed. The isodose curve chosen to prescribe the dose is 3 mm to 5 mm away from the skin surface. Three fractions of 8Gy are scheduled, 1 week apart, delivering a radiobiological equivalent of 48Gy of standard radiotherapy within 2 weeks. Our preliminary experience shows excellent early skin tolerance. The study is ongoing to assess efficacy and late effects.

Emerging Opportunities of Radiotherapy Combined With Immunotherapy in the Era of Breast Cancer Heterogeneity.

The association of radiotherapy and immunotherapy has recently emerged as an exciting combination that might improve outcomes in many solid tumor settings. In the context of breast cancer, this opportunity is promising and under investigation. Given the heterogeneity of breast cancer, it might be meaningful to study the association of radiotherapy and immunotherapy distinctly among the various breast cancer subtypes. The use of biomarkers, such as tumor infiltrating lymphocytes, which are also associated to breast cancer heterogeneity, might provide an opportunity for tailored studies. This review highlights current knowledge of the association of radiotherapy and immunotherapy in the setting of breast cancer and attempts to highlight the therapeutic opportunities among breast cancer heterogeneity.

Metabolic functional imaging for tumor radiosensitivity monitoring.

Assessing tumor radiosensitivity before and during radiation therapy can be a crucial element in decision-making with regard to treatment. However, no known non-invasive test is available at present, which allows for a reliable evaluation of the radiosensitivity of a tissue subjected to radiotherapy. Among tests being evaluated, positron emission tomography (PET) is considered to be a promising method. The purpose of this review is to identify the tests and research paths that have recently been explored for the evaluation of tumor response to treatment after isotopic labeling revealed by nuclear imaging. The majority of the explored methodologies are based on the indirect evaluation of the radiosensitivity by cell proliferation or apoptosis, tissue oxygenation or hypoxia, intrinsic radiosensitivity of clonogenic cells, tumor metabolism and angiogenesis. The development of such methods would permit the adoption of a therapeutic regimen with respect to a given radiosensitivity of a tissue. Therefore, a given therapeutic strategy could be readjusted (by associating, for instance, a radiosensitizer of hypoxic cells) or even modified if it proved to be inadequate or when it presents an unfavorable cost-effectiveness ratio. We present here a critical review of the radiotracers revealed by nuclear imaging that are developed for radiosensitivity monitoring.

How could breast cancer molecular features contribute to locoregional treatment decision making?

Systemic treatments are tailored to breast cancer (BC) heterogeneity, which is not yet taken into account for radiotherapy (RT) personalization. The primary objective of this review is to summarize existing data suggesting BC subtypes and genetic assays are prognostic and predictive biomarkers useful for RT decision-making and to provide implications for their incorporation into future translational and clinical research. The evidence suggesting that BC subtypes also exhibit distinct "locoregional recurrence (LRR)" patterns is retrospective but consistent and validated in over fifteen studies. The HER-2 positive and triple negative subtypes are the most susceptible to locoregional failure. The high risk of the HER-2 positive subtype can be reversed with trastuzumab administration. Very little is known on the subtypes' intrinsic radiosensitivity properties. Genetic assays have assessed retrospectively signatures' prognostic and predictive value in patients' cohorts (several coming from prospective studies) for LRR risk and radiotherapy (RT) benefit. Further confirmation is needed before their introduction into clinical routine. Evidence on the use of molecular biomarkers for adjuvant RT tailoring is emerging but needs validation and introduction into prospective studies. The plethora of modern RT options (partial breast irradiation, hypofractionation), as well as recent evidence pointing towards more extensive radiotherapy, demand introduction of biological features into clinical trials to improve therapeutic decisions. Open questions, such as tailoring of irradiation after neo-adjuvant chemotherapy in complete responders and the understanding of the interplay between local control, systemic recurrence and survival given modern systemic treatments, need to be addressed under the prism of biology within this heterogeneous disease. Intrinsic radiobiological properties within this heterogeneity need to be highlighted in order to further improve outcomes.